The present disclosure relates to electronic circuits and methods, and in particular, to switched capacitor transmitter circuits and methods.
Digital transmission involves the physical transfer of data (a digital bit stream or a digitized analog signal) between electronic systems. FIG. 1 illustrates a typical arrangement for transmitting data between two electronic systems. Electronic system 101 may include digital processing circuits 110 (e.g., a CPU and memory) storing digital data 112. Electronic system 101 may send digital data 112 to another electronic system 102 using a transmitter (Tx) 114. Transmitter 114 receives the digital data 112 and converts the digital data into an analog signal for transmission across a communication medium 103. In a wireless application, analog signals may be upconverted to radio frequency signals and then broadcast between antennas through the air, for example. Electronic system 102 includes a receiver 124 (Rx) for receiving the digital data 112. In this example, electronic systems 101 and 102 can both send data using a transmitter (Tx) and receive data using a receiver (Rx). Accordingly, electronic system 102 may also include digital processing circuits 120 storing digital data 122 that may be sent to electronic system 101 using transmitter 124, for example.
FIG. 2 illustrates an example prior art architecture for transmitting data in a wireless channel. In a wireless transmission channel, a digital data signal comprising encoded data is converted to an analog signal using a digital-to-analog converter (DAC) 201. The analog signal (or analog “baseband” signal) is then processed using a low pass filter (LPF) 202 and gain stage (Av) 203. The analog baseband signal is thenshifted to a carrier frequency using up-converter 204 and a local oscillator (LO). The up-converted signal is filtered again at 205. A power amplifier 206 increases the power of the analog signal for transmission across the communication medium.
Power consumption is a significant problem in contemporary transmission systems. The rapid expansion of communication systems, such as wireless devices, has tightened the power consumption requirements of devices, and transmitters are a large source of such consumption. Traditional analog power amplifiers, for example, consume particularly large amounts of power. Improving the efficiency of such analog power amplifiers is an area of continued research.